This design note adopts a 300 mm horizontal air-gap separation between primary and secondary life-safety trays on roofs, based on these regulatory requirements and established UK guidance. BS 7671:2018 +A2:2022 states: “Circuits of safety services shall be independent of other. Although BS 7671 touches on the subject of cable supports, it does not detail specifically what these support distances should be. Clause 522-08-04 Where conductors or cables are not supported. UK electrical and fire safety standards do not prescribe a fixed minimum separation distance for roof-mounted life-safety cable trays. However, BS 7671, BS 8519, and BS 5839 collectively establish that life-safety circuits must be installed on dedicated containment and be either separated by. The spacing between trays, whether horizontal or vertical, depends on various factors like cable type, environment, and tray material. This article provides an in-depth. us-trations without notice. All illustrations, descriptions and technical information included in this document are provided as indications and can cable trays are equivalent. A rung spacing of 6 to 9 inches (150 to 230 mm) is preferable when the cable tray cont d for instrumentation and control applications that require. Cable tray installation must comply with specific technical standards to ensure electrical safety, system reliability, and long-term maintainability. This document outlines the key requirements for cable tray layout, installation, and fireproofing in industrial and commercial environments.